a. Field of the Invention
The present invention relates generally to cargo lifts for aircraft, and, more particularly, to an internal cargo lift for raising/lowering cargo between decks of an aircraft that allows for convenient and rapid conversion of passenger seating areas or other previously unusable areas to cargo carriage space and back.
b. Related Art
Historically, the commercial aircraft industry has distinguished between passenger and cargo aircraft, i.e., certain aircraft are dedicated to passenger travel while others are used solely for transportation of cargo. However, given the inflexibility inherent in dedicating an aircraft to one service or the other has become a significant problem with increasing competitiveness in the industry. A limited number of aircraft have been configured as “combis”, that are able to carry a load of passengers and commercial cargo, but few of these have been flexible designs that allow the respective areas devoted to seating and cargo to be varied. Moreover, in those few cases where the configuration can be adjusted, conversion of the spaces has been exceedingly time-consuming and difficult.
A related problem is the difficulty in delivering the palletized cargo to the main (passenger) deck of the aircraft, even if this area is cleared of seating. In a passenger aircraft, cargo is ordinarily carried in palletized form in lower deck cargo compartments. Typically, there is a compartment fore and aft of the wing intersection/wheel well area, with each cargo compartment being serviced by a door on the lower lobe. Various types of ULDs (unit load devices) are carried in the compartments; depending on aircraft type and cargo, the ULDs may have a single line or “two abreast” configuration.
The advent of next-day delivery (and even same day delivery) of packages has increased the value of available cargo space. This is increasingly true in the case of regular passenger aircraft, due to the frequency of flights made to numerous destinations, as opposed to the hub-and-spoke operations to which classical daily/overnight freight operators have been wedded.
In some instances, an increased allowance for carry-on baggage has freed up lower deck cargo space and has allowed expanded cargo service on passenger aircraft. However, aircraft size (i.e., the number of seats) must be matched to the economics of a particular route. Thus, a bigger aircraft, with a larger lower lobe capacity, cannot be economically placed on a route if its seats are not also filled to an adequate extent. Thus, the ability to carry high-value extra cargo is still limited.
Removing a portion of the seating and carrying additional ULDs on the main deck is an attractive option, however, it has heretofore been largely impractical. Carriage of ULDs on the main deck has historically required adding a large cargo door in the upper part of the fuselage, allowing direct access to the main deck: this is a major structural modification, requiring extensive reinforcement, costs and regulatory approval difficulties which negate feasibility.
An alternative would be to transfer cargo from the lower lobe to the main deck (or to the two upper decks in the case of “double decker” jumbo aircraft), since the lower deck already has a cargo door, thus eliminating the requirement for a new main deck door. However, there has heretofore been no satisfactory mechanism for transferring ULDs from the lower lobe to the passenger deck/decks and vice versa. Moreover, the installation of such a mechanism, when modifying an existing passenger aircraft, presents the potential for structural, regulatory and cost problems similar to those involved in installing an upper deck cargo door.
In addition to passenger aircraft, related problems exist in certain dedicated cargo aircraft, notably double-decker “jumbo” aircraft that have been converted to full-time cargo use. For example, 747 cargo aircraft generally transport cargo on the main deck, that in conventional aircraft would carry passengers, but the difficulty in raising cargo to the upper deck in the forward position of the fuselage means that this part of the aircraft goes largely unused.
Accordingly, there exists a need for an apparatus for efficiently transferring cargo ULDs between the lower area and upper deck or decks of an aircraft, so as to obviate the need to add a large cargo door in the upper part of the fuselage. Furthermore, there exists a need for such an apparatus that does not require major structural modifications of the aircraft that would involve excessive expense and regulatory review. Still further, there exists a need for such an apparatus that, in itself, is comparatively economical, and that is physically compact so as to avoid significantly compromising the availability of space within the passenger and cargo areas of the aircraft. Still further, there exists a need for such an apparatus that is light in weight and does not require power systems that would add significant weight and cost to the aircraft in which the apparatus is installed. Still further, there exists a need for such an apparatus that operates with sufficient rapidity to avoid adding excessive time to loading/unloading operations and turnaround of the aircraft in service.